UHPLC-MS/MS Approach for Following Nimodipine Saturation Kinetics in Acute Rat Brain Slice

Nimodipine (NMD) has gained increasing attention in the latest scientific studies as it can act alone or in combination with other drugs to relieve or prevent symptoms of traumatic brain injury, ischemic stroke, and migraine or even to improve pregnancy outcomes. During an acute stroke, an altered cerebral metabolic rate results in a pH change in the affected brain region. However, the effect of pH changes on NMD penetration into the brain tissue has not been investigated yet. Only a few papers reported the determination of NMD concentration in the brain tissue. They usually required a relatively large volume of brain homogenate, and only one of them used mass spectrometric detection. Therefore, we aimed to develop, validate, and apply our new targeted method for studying the pharmacokinetics of NMD at different pH conditions in acute rat brain tissue as a model of cerebral ischemia. Herein, we present a fully validated targeted ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method with a five-minute total run time for the quantitation of NMD in rat brain tissue using a low quantity of brain homogenate. A matrix match external calibration procedure was applied for quantitative measurement using a stable isotope-labeled NMD internal standard. The new sample preparation procedure resulted in high recoveries (96.9-110.6%) in brain homogenate with negligible matrix effect (-9-12.9%). The lower limit of detection of NMD was 15 ng/g brain (547 fg of NMD injected into the column). In acute rat brain tissue, the maximum median concentrations of NMD (cmax: 31.93 mu g/g (pH 7.38), 46.16 mu g/g (pH 6.50), 30.89 mu g/g (pH 7.57) were reached at 50 min (tmax).